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Wind Speed vs. Landing Difficulty


FlyingMonkey

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When Bill Ince and I were returning from our Page Expedition, we had the opportunity to encounter several different instances of "challenging" conditions.  Two of them really seem to invite comparison and discussion.

 

First, when we landed at Beaumont, TX  (KBPT), we had a lot of turbulence and howling winds.  We actually were trying to make KHUM, but called it quits due to turbulence and marginal visibility.  The final wind check on approach showed winds 24G32, *far* more than I had previously landed in.  Thankfully the wind was within 10° of alignment with the runway (one of the reasons we chose that airport for our diversion).  

 

In spite of the high winds, Bill and I both made stable approaches and good landings.  I used 0° flaps and landed faster than normal.  This worked well, but just at touch down a gust picked me back up a few feet.  I added a slight amount of power so I would not stop flying suddenly, and let the airplane settle back to the runway.  There was no drama.  Overall I was *very* happy with the landing, considering the conditions.

 

The second situation was when we landed at Defuniak Springs, FL (54J) two days later.  The flight was smooth at 5500-7500ft, and for once the visibility was good.  Our planned landing was for Crestview (KCEW), but the wind was showing 12-14kt almost 90° to the only runway, so we went to 54J where the wind was once again within 10° of the runway heading.  Final wind check on approach was 09G14.

 

No problem...if we can land 24G32, then 09G14 should be a snap, right?  WRONG!

 

I don't think I ever "stirred the stick" in a landing more than I did on that one.  I used 15° flaps, and had at least 80% aileron deflections in both directions on short final and all the way into the touchdown.  The actual landing was good, but it was a LOT of work and I was close to a go-around.  As I was taxiing in to park I saw the windsock straight out pointed down the runway, then swinging to direct crosswind one way, and then completely opposite.  So instead of of 09G14 aligned with the runway, it was really 09G14 variable within 180° arc, a *totally* different story!  Once parked Bill and I both marveled at how challenging the landings were.

 

The point of this comparison?  Just to say that the reported conditions are not always the whole story.  Every approach is different, and you can't tell how tough a situation actually is until you attempt the landing.  In the first case above, the extremely high winds sounded scary, but in reality the stability of the wind direction made the landing only moderately difficult.  In the second case the winds were far weaker, but the instability of the wind direction made for a very challenging approach and landing.  If we combined those two events, the 24G32 wind at KBPT and the huge directional swings at 54J, I think that would be a nearly "unlandable" situation for the CT.  At least at my skill level!

 

Discuss.  :) 

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When Bill Ince and I were returning from our Page Expedition, we had the opportunity to encounter several different instances of "challenging" conditions.  Two of them really seem to invite comparison and discussion.

 

First, when we landed at Beaumont, TX  (KBPT), we had a lot of turbulence and howling winds.  We actually were trying to make KHUM, but called it quits due to turbulence and marginal visibility.  The final wind check on approach showed winds 24G32, *far* more than I had previously landed in.  Thankfully the wind was within 10° of alignment with the runway (one of the reasons we chose that airport for our diversion).  

 

In spite of the high winds, Bill and I both made stable approaches and good landings.  I used 0° flaps and landed faster than normal.  This worked well, but just at touch down a gust picked me back up a few feet.  I added a slight amount of power so I would not stop flying suddenly, and let the airplane settle back to the runway.  There was no drama.  Overall I was *very* happy with the landing, considering the conditions.

 

The second situation was when we landed at Defuniak Springs, FL (54J) two days later.  The flight was smooth at 5500-7500ft, and for once the visibility was good.  Our planned landing was for Crestview (KCEW), but the wind was showing 12-14kt almost 90° to the only runway, so we went to 54J where the wind was once again within 10° of the runway heading.  Final wind check on approach was 09G14.

 

No problem...if we can land 24G32, then 09G14 should be a snap, right?  WRONG!

 

I don't think I ever "stirred the stick" in a landing more than I did on that one.  I used 15° flaps, and had at least 80% aileron deflections in both directions on short final and all the way into the touchdown.  The actual landing was good, but it was a LOT of work and I was close to a go-around.  As I was taxiing in to park I saw the windsock straight out pointed down the runway, then swinging to direct crosswind one way, and then completely opposite.  So instead of of 09G14 aligned with the runway, it was really 09G14 variable within 180° arc, a *totally* different story!  Once parked Bill and I both marveled at how challenging the landings were.

 

The point of this comparison?  Just to say that the reported conditions are not always the whole story.  Every approach is different, and you can't tell how tough a situation actually is until you attempt the landing.  In the first case above, the extremely high winds sounded scary, but in reality the stability of the wind direction made the landing only moderately difficult.  In the second case the winds were far weaker, but the instability of the wind direction made for a very challenging approach and landing.  If we combined those two events, the 24G32 wind at KBPT and the huge directional swings at 54J, I think that would be a nearly "unlandable" situation for the CT.  At least at my skill level!

 

Discuss.   :)

 

Yes , I find that for me , in the state of Florida, Summer usually bring calm winds (unless you are in the middle of a thunderstorm), so I generally use 15 degrees of Flaps for landing. In the Fall , Winter , and Spring winds are , generally stronger and variable, so I use 0 degree flaps, to land. This gives me more directional stability. Once I used -6 degree Flaps in 20 knot winds. If the winds are 10 Knots or more (in any direction) , I use 0 Flaps. This works well for me.

 

Cheers

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There seems to be a false notion, that somehow, flap settings affect directional stability. Actually, they do not.

Increased directional control comes from "increased relative speed (wind) over the vertical stabilizer and rudder." The more speed over the rudder surface, at a given angle, the more authority around the vertical axis. Generally, decreased flap settings warrant a slightly higher Vref, thus, more rudder authority is available.

 

You just made the case for not doing stall landings.  The faster you go, the more stable you are....

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There seems to be a false notion, that somehow, flap settings affect directional stability. Actually, they do not.

Increased directional control comes from "increased relative speed (wind) over the vertical stabilizer and rudder." The more speed over the rudder surface, at a given angle, the more authority around the vertical axis. Generally, decreased flap settings warrant a slightly higher Vref, thus, more rudder authority is available.

 

In the CT series though, increased flap settings do affect roll authority more than with some airplanes, because of the drooping ailerons (flaperons).  In addition to being slower and having less air over the surfaces, the ailerons have less available deflection.  Normally you'd run out of rudder before you run out of aileron, even with the flaperons, but with big side gusts I could see a possibility of having insufficient roll authority to counter it with larger flap settings dialed in.  I have had strong gusts that required large stick deflections to counter with 30° flaps in a couple of times.

 

The advantage of the flaperons is that the ailerons add to the effective area of the flaps, giving more lift and slower approach speeds.  The RV-12 takes this a step further with full flaperons that serve both purposes. 

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You just made the case for not doing stall landings.  The faster you go, the more stable you are....

 

I don't think that case has been made quite the way you're describing.  I think the case is made for using the speed and and configuration "appropriate to conditions".  Speed on landing is kind of like a doctor prescribing a drug with strong side-effects:  he uses the minimum dosage of the drug required to obtain the desired effect.  

 

Speed on landing works the same.  Use the minimum speed required to affect a safe and stable landing.  Sometimes that will take a little more, sometimes less.  IMO as always with landing technique discussions.  :)

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:)

No, that's not what I said at all.

The faster you go, the more rudder authority you have. Right?

 

I agree. By extension the opposite must be true, the slower you go the less rudder/aileron authority you get...  We now wait to see how CT reacts.  Laughing...

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Authority and stability are not the same things.  

 

Crisp controls at touchdown with wind shear means the riskiest moments are yet to come.

 

When gusts are an issue, you are vulnerable when you are too fast to have enough weight on your gear to overcome a gust with malevolent intent and yet too slow to overcome said gust with flight controls.  If you land with excess speed you will go through this vulnerable speed zone with gear on the runway and if the gust wins you will lose directional control and will likely be skidding sideways.

 

If you take the same scenario where the malevolent gust is going to overcome you at the worst moment / speed where you cannot overcome it but without the excess speed then the point where you are overcome is likely to be prior to touchdown and its much more likely that a go-around can be initiated.

 

Certainly there is a little overlap but by minimizing my speed I find if I do get screwed up due to gusts I can flyaway as opposed to skidding off the runway. 

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Vulnerable speed zone and crosswind takeoffs

 

The vulnerable speed where winds can overcome control authority is an issue on take off as well.  I recall a flight to Oregon from Mammoth Lakes California, a flight of 2 CTSWs.

 

We landed midway at Alturas, CA landing to the east into a big easterly wind.  We had a pee and talked a while with Tom Dunham the then Airport manager as well as Flight Design West's A&P as well as check out pilot.

 

Takeoffs to the east where prohibited so we used the south crosswind runway and did crosswind takeoffs.  The other CT went 1st and even with a stiff 90 degree left crosswind the pilot used a normal takeoff technique with a little backpressure until the CT took off on its own.  As he approached flying speed with his nose wheel light or in the air he began to skid from the centerline all the way to the runway edge.  It looked like he would crash for sure but managed to get airborne in the last possible second.

 

I departed next and did it without any back-pressure, even a little forward pressure to keep me on the ground until I had flying speed plus a few knots so that my rotation would be instant and without any loss of directional control.  Easy peasy.

 

Take offs are easier and are better if we accelerate beyond the vulnerable speed before rotating but take off or landing that vulnerable speed where our grip on the runway can be overcome and our control authority can be over come as well is a zone that we should transition with the cards stacked in our favor.  On take off I wait till I"m fast enough and on landing I wait till I'm slow enough in both cases giving me the best chance to abort before loss of control. 

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Speed on landing is kind of like a doctor prescribing a drug with strong side-effects: he uses the minimum dosage of the drug required to obtain the desired effect.

 

 

I like the analogy.

 

With gusty conditions, we may want to approach just a tad faster. But remember, the rule is 1/2 the gust factor added to the normal approach speed.

 

And I don't think the primary reason has ever been control authority, at least not directly.

 

Imagine a plane that stalls at 40k with full flaps. 1.3vso would be 52k, a typically recommended approach speed.

 

Now imagine landing with 10G22. Further imagine using 52k. And then imagine an extended 22k gust, where the plane momentarily stabilizes. So far, so good.

 

Until the wind drops to 10k again, resulting in a momentary loss of 12k, from 52k to 40k. OOPS!

 

That's why an experienced pilot would have increased his speed by 6k, 1/2 the 12k gust factor. That additional margin at 58k would avoid the stall that 52k might have led to.

 

Yes, even more speed would give even more cushion, but as CT points out the plane still has to transition through the vulnerable range one way or another. And the really excessive speeds I often see, often with little or no flaps, result in a huge increase in the amount of energy carried, sometimes with disastrous effects.

 

For me, I'll carry full flaps in my Sky Arrow unless it's terribly gusty, and then use 20°. Maybe even 10° if I find myself in a situation I have no business being in. And that is done for control effectiveness - it doesn't effect margin over the stall substantialyl, since the stall speed itself goes up with the lesser flap settings.

 

Oh, and the "Laughing..." comment has no place in an informed discussion among pilots, some of who have been around the block a time or two, and don't need a neophyte's sarcasm.

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Oh, and the "Laughing..." comment has no place in an informed discussion among pilots, some of who have been around the block a time or two, and don't need a neophyte's sarcasm.

 

"neophyte's sarcasm" = weak attempt to make a personal attack.

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Authority and stability are not the same things.  

 

Crisp controls at touchdown with wind shear means the riskiest moments are yet to come.

 

When gusts are an issue, you are vulnerable when you are too fast to have enough weight on your gear to overcome a gust with malevolent intent and yet too slow to overcome said gust with flight controls.  If you land with excess speed you will go through this vulnerable speed zone with gear on the runway and if the gust wins you will lose directional control and will likely be skidding sideways.

 

If you take the same scenario where the malevolent gust is going to overcome you at the worst moment / speed where you cannot overcome it but without the excess speed then the point where you are overcome is likely to be prior to touchdown and its much more likely that a go-around can be initiated.

 

Certainly there is a little overlap but by minimizing my speed I find if I do get screwed up due to gusts I can flyaway as opposed to skidding off the runway. 

 

 

CT, that's a good, succinct argument for your style of landing in difficult conditions.  Your breakdown of the phases is helpful.

 

 Having said that, it occurs to me that your two posts might actually scuttle your entire reasoning.

 

Couldn't the boys who like to land fast replicate your tactics at Alturas in order to get weight on the wheels while still going fast, and keep it there until stopped?  This would give them crisper handling in the air but with no disadvantage during the 'vulnerable speed zone' on the roll out. 

 

In that case, wouldn't you be better off with a fast landing as you can have the best of both worlds: lots of authority right up to touchdown, yet with no vulnerable phase on the tarmac during the roll out?

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Al,

 

Getting weight on all wheels during landing, in gusty conditions means forward stick pressure.  This can work well but the risk is wheelbarrowing.  Imagine that you use this technique at the same time that a gust raises your tail, you are now out of control.

 

I've had this happen to me and the lesson I've learned is that I have to maintain pitch attitude even after touchdown.

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Gusty and variable direction winds can certainly be challenging in the CT.  Add thermal activity and windshear and you have a lot of stick work to do!  After about 2000hrs of CT flying in these type of conditions including winds as high as 40kts, using lower flap settings and an approach speed appropriate to the configuration and gust factor is the way to go.  If I have crosswinds or gust factors greater than 10kts or a lot of thermal activity I opt for 0 deg flap approaches. 

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Al,

 

Getting weight on all wheels during landing, in gusty conditions means forward stick pressure.  This can work well but the risk is wheelbarrowing.  Imagine that you use this technique at the same time that a gust raises your tail, you are now out of control.

 

I've had this happen to me and the lesson I've learned is that I have to maintain pitch attitude even after touchdown.

 

CT,  a few months ago I was bringing the plane back from Vegas and had to land in about 25kt winds...maybe about 13 or so of it was a 30 degree xwind. 

 

The first pass was ugly, the plane touched on one, then two wheels and started to fly again so I went around. 

 

The second pass I got the mains on the runway and pushed the stick forward quickly to get the nosewheel down and try and stay on the runway.  It worked but it was a palm-sweating ordeal.  I had a tough time keeping the plane taxiing in that wind but did manage to get it into the hangar.     It was not fun.

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Vulnerable speed zone and crosswind takeoffs

 

The vulnerable speed where winds can overcome control authority is an issue on take off as well. I recall a flight to Oregon from Mammoth Lakes California, a flight of 2 CTSWs.

 

We landed midway at Alturas, CA landing to the east into a big easterly wind. We had a pee and talked a while with Tom Dunham the then Airport manager as well as Flight Design West's A&P as well as check out pilot.

 

Takeoffs to the east where prohibited so we used the south crosswind runway and did crosswind takeoffs. The other CT went 1st and even with a stiff 90 degree left crosswind the pilot used a normal takeoff technique with a little backpressure until the CT took off on its own. As he approached flying speed with his nose wheel light or in the air he began to skid from the centerline all the way to the runway edge. It looked like he would crash for sure but managed to get airborne in the last possible second.

 

I departed next and did it without any back-pressure, even a little forward pressure to keep me on the ground until I had flying speed plus a few knots so that my rotation would be instant and without any loss of directional control. Easy peasy.

 

Take offs are easier and are better if we accelerate beyond the vulnerable speed before rotating but take off or landing that vulnerable speed where our grip on the runway can be overcome and our control authority can be over come as well is a zone that we should transition with the cards stacked in our favor. On take off I wait till I"m fast enough and on landing I wait till I'm slow enough in both cases giving me the best chance to abort before loss of control.

Good stuff CT, thanks. I have not encountered this yet. I hope I have the presence of mind to remember this when I do.

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CT,  a few months ago I was bringing the plane back from Vegas and had to land in about 25kt winds...maybe about 13 or so of it was a 30 degree xwind. 

 

The first pass was ugly, the plane touched on one, then two wheels and started to fly again so I went around. 

 

The second pass I got the mains on the runway and pushed the stick forward quickly to get the nosewheel down and try and stay on the runway.  It worked but it was a palm-sweating ordeal.  I had a tough time keeping the plane taxiing in that wind but did manage to get it into the hangar.     It was not fun.

 

I have a different mind set.  In winds like that I don't want to land fast but I don't mind getting one wheel to contact while I am still fast.  Sometimes I am tracking the centerline but I'm not well aligned until I get one  wheel on the runway.  Being a nose dragger the CT tends to align itself while you hold the other main off.

 

One wheel down without good alignment can work easily but both mains down without alignment is where loss of control begins.  All 3 down without alignment and you are trying to turn at high speed, not good.

 

On your first attempt after getting both mains down you went flying again, this suggests excess speed.  I'm not in a hurry to allow my 2nd main to settle its better to counter the drift with aileron till you can't hold wing low any longer due to speed decaying.  Then the nose, I want to keep a landing attitude till I get slow, If I allow the nose wheel to settle early it may not be pointed down the runway due to the cross controlled inputs.

 

Before my nose settles I am aware of my alignment but not necessarily my rudder deflection needed for that alignment and therefore I'm not aware of where my nose wheel is pointed.  If I get the stick full aft and let it settle at a slow speed it becomes a non issue but allowing it to settle at a high speed can mean an unwanted turn.

 

I remember long ago in my Skyhawk getting all 3 wheels on the runway while still fast and then the inevitable gust felt as though it lifted my tail and I was then headed off the runway on my nosewheel only.  I was headed off the runway and was also headed for a prop strike.  Pulling back seemed counter intuitive to me back then but now I see it as a need to continue to fly the airplane especially on gusty days.  After that I want my nose up till I'm slow.

 

On the worst crosswind landing days the hardest part might be exiting the runway.  If that turn is not into the wind you might want to go the other way if possible.  I have once before at Mammoth called Unicom and asked for help holding my wings down as I turned off the runway.

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For one wheel touchdown, misaligned with the runway in a crosswind, I think it matters *how* you are misaligned.  If you are misaligned with your nose pointed into the wind, the extra rolling friction can act like a pivot and help you get aligned.  If you are misaligned with your nose pointed the other way, that extra rolling friction is going to help you weathervane and make your landing much more difficult.

 

If your alignment is off more than a few degrees in a crosswind, it's probably better just to go around and get better aligned next time.  Unless you are using the Fast Eddie "angle across the runway to reduce the effective crosswind" technique.

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Thanks for all the advice on windy/gusty landings with the CT - most appreciated.

Gusty is the middle name of Irish weather, and when you couple that with our narrow and short airstrips, it's a significant issue here.

That's the primary reason why the CT has never really caught on here - lots of runway excursions in the early days led to negative reports and high insurance premiums.

Unfortunate.

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For one wheel touchdown, misaligned with the runway in a crosswind, I think it matters *how* you are misaligned.  If you are misaligned with your nose pointed into the wind, the extra rolling friction can act like a pivot and help you get aligned.  If you are misaligned with your nose pointed the other way, that extra rolling friction is going to help you weathervane and make your landing much more difficult.

 

 

Tricycle gear aircraft have their center of mass between the mains and the nose wheel and naturally want to align as opposed to tail wheel aircraft that naturally want to swap ends.

 

If as you say your nose is pointed the other way (downwind) you will weather-vane that would fix things no?

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Tricycle gear aircraft have their center of mass between the mains and the nose wheel and naturally want to align as opposed to tail wheel aircraft that naturally want to swap ends.

 

If as you say your nose is pointed the other way (downwind) you will weather-vane that would fix things no?

 

I misspoke...I actually meant align the plane with the wind, not into the wind (weathervane)...sorry for the confusion.

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I misspoke...I actually meant align the plane with the wind, not into the wind (weathervane)...sorry for the confusion.

 

Same thing.  Its a matter of geometry and where center of mass is,

 

If you land in wind shear similar to what Mammoth sees over the runway about 100 days a year even with perfect alignment you may lose it as you settle.

 

When I hit the shear all aligned and a result is a wing drop my reaction is to control and soften that drop with opposite rudder.  It feels like 'walking' it on where the first step is the dropped wing / gear contact, next step is re-alignment and third step is the other main coming down after alignment.  Using the rudder in this manner as well as wing dropping can mess with the alignment even if you are tracking the centerline.

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Tricycle gear aircraft have their center of mass between the mains and the nose wheel and naturally want to align as opposed to tail wheel aircraft that naturally want to swap ends.

 

If as you say your nose is pointed the other way (downwind) you will weather-vane that would fix things no?

 

As long as you touch one or both mains  the velocity vector setup on approach will make sure you go where you were flying prior to touchdown.  The easy way to get off the runway other than being kicked to the side by a gust is to touch the nosewheel first.  Then you end up wheelbarrowing off or worse.

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As long as you touch one or both mains  the velocity vector setup on approach will make sure you go where you were flying prior to touchdown.  The ONLY way you can get off the runway other than being kicked to the side by a gust is to touch the nosewheel first.  Then you end up wheelbarrowing off or worse.

 

Your are correct (tricycle gear) with certain exceptions.  

  • asymmetric brake
  • nose-wheel steering failure
  • loss of directional control due to the effects of Aquaplaning
  • landing on flat tire
  • gear failure
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